Woocommerce Ajax not loading after changing site address url

Job Description

I have a wordpress ecommerce website that I'm using woo commerce plugin with, my client asked me to add an intro so I did but in order to do so I have to change the Site Address URL in wordpress settings to a different url than the wordpress url, and when i did that the shopping cart stopped updating and also the checkout pages is giving me an error Sorry, your session has expired. Return to homepage.

I'm not very experienced in this but I know its just a simple code that needs to be added to the function.

I'm welling to pay $10 for the 1st person who will send me the working code.
Here is the site: lexisvip.com also please see attachments.
Thank you